TOBRADEX
Clinical safety rating: caution
Comprehensive clinical and safety monograph for TOBRADEX (TOBRADEX).
Tobradex is a combination of tobramycin (an aminoglycoside antibiotic) and dexamethasone (a corticosteroid). Tobramycin inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit, causing misreading of mRNA and cell death. Dexamethasone suppresses inflammation by inhibiting phospholipase A2, reducing prostaglandin and leukotriene synthesis, and decreasing cytokine production.
| Metabolism | Tobramycin is not metabolized; primarily excreted unchanged in urine. Dexamethasone is metabolized in the liver via CYP3A4 to inactive metabolites. |
| Excretion | Tobramycin: ~90% renal (glomerular filtration), <1% biliary. Dexamethasone: hepatic metabolism, metabolites renally excreted. |
| Half-life | Tobramycin: 2-3 hours in adults with normal renal function; prolonged to 24-60 hours in anuria. Dexamethasone: 36-54 hours. |
| Protein binding | Tobramycin: <10% bound to plasma proteins. Dexamethasone: ~77% bound, primarily to albumin. |
| Volume of Distribution | Tobramycin: 0.26 L/kg (extracellular fluid compartment). Dexamethasone: 0.75-1.3 L/kg. |
| Bioavailability | Ophthalmic: limited systemic absorption via cornea; approximately 50% of topically applied tobramycin is absorbed through the cornea, but systemic bioavailability is very low due to drainage and dilution. |
| Onset of Action | Ophthalmic: antibacterial effect within hours after topical application; anti-inflammatory effect within 24 hours. |
| Duration of Action | Ophthalmic: dosing every 4-6 hours for anti-inflammatory effect; antibacterial duration depends on concentration above MIC. |
| Molecular Weight | Tobramycin: 467.51 Da; Dexamethasone: 392.46 Da |
1-2 drops into the affected eye(s) every 4-6 hours; in severe disease, every 1-2 hours initially, then taper. Ointment: apply a 1/2-inch ribbon into the conjunctival sac 3-4 times daily.
| Dosage form | OINTMENT |
| Renal impairment | No adjustment required for ophthalmic use. |
| Liver impairment | No adjustment required for ophthalmic use. |
| Pediatric use | Same as adult dosing for children ≥2 years; use dose per weight not established, clinical judgment advised. |
| Geriatric use | No specific adjustment; use with caution due to increased risk of intraocular pressure elevation and infection. |
| 1st trimester | Avoid unless benefit outweighs risk; corticosteroids may cause cleft palate (rare) and aminoglycosides may carry ototoxicity risk. |
| 2nd trimester | Use only if clearly needed; monitor fetal growth with prolonged use. |
| 3rd trimester | Use with caution; prolonged corticosteroid use may cause adrenal suppression in neonate. |
Clinical note
Comprehensive clinical and safety monograph for TOBRADEX (TOBRADEX).
| Placental transfer | Both tobramycin and dexamethasone cross the placenta; degree is dose-dependent but systemic absorption from ophthalmic use is low. |
| Breastfeeding | Systemic absorption from topical ophthalmic use is minimal; however, consider the potential for infant exposure. Use caution if nursing. |
| Lactation Rating |
■ FDA Black Box Warning
Not applicable; no FDA black box warning exists for Tobradex.
| Serious Effects |
Hypersensitivity to any componentFungal infections of the eyeUntreated bacterial eye infectionsHerpes simplex keratitisViral infections of the cornea or conjunctiva
| Precautions | Prolonged use may lead to ocular hypertension/glaucoma, Secondary ocular infections (fungal, viral) may develop, Corneal perforation risk in patients with corneal thinning, Systemic absorption may occur with prolonged use, Not for use in fungal or viral infections of the eye |
| Food/Dietary | None known. No dietary restrictions are required for ophthalmic use. Systemic interactions are negligible due to minimal absorption. |
Loading safety data…
| L3 (Moderately Safe) |
| Teratogenic Risk | Corticosteroids are associated with increased risk of cleft palate (first trimester) and fetal adrenal insufficiency (chronic use). Tobramycin is an aminoglycoside; risk of ototoxicity and nephrotoxicity is theoretical but not confirmed at typical ophthalmic doses. Avoid systemic exposure; topical ophthalmic use has minimal systemic absorption, but risk cannot be completely excluded. |
| Fetal Monitoring | No specific monitoring required for topical ophthalmic use. If used long-term or in high doses, consider fetal ultrasound for growth and adrenal function. |
| Fertility Effects | No known effects on fertility from topical ophthalmic use. |
| Clinical Pearls |
| TOBRADEX (tobramycin/dexamethasone) is a fixed-dose combination of an aminoglycoside antibiotic and a corticosteroid for ophthalmic use. Shake well before each use. To minimize systemic absorption, apply gentle pressure to the nasolacrimal duct for 1 minute after instillation. Monitor for secondary infection, corneal thinning, or increased intraocular pressure with prolonged use. Avoid use in viral keratitis, mycobacterial infections, or fungal diseases. |
| Patient Advice | Shake the bottle vigorously before each use. · Do not touch the dropper tip to your eye or any surface to avoid contamination. · Remove contact lenses before using and wait at least 15 minutes before reinserting. · If you use more than one eye drop, wait at least 5 minutes between medications. · Use only as directed; do not exceed the prescribed duration. Prolonged use may increase eye pressure or lead to infection. · Contact your doctor if you experience eye pain, vision changes, or worsening redness. |